I finally made the upgrade to a 3G alternator. I got a 94-95 Mustang 130 amp unit, upgraded the wiring, and 4g wire with 200 amp fuse. After the install, I started the car up and there was a loud metal-on-metal sounding screech for about 1-2 seconds and then it went away and runs completely normal with no noises. The range indicator on the belt tensioner was right at the edge, so I replaced the belt with another belt that is 90" long. The range indicator moved closer to the center, but the screeching is still there when the car starts. I am running the original pulley from the old alternator. I originally had the pulley that came with the alternator, it made the same noise as well. The belt looks to be aligned properly with the pulleys. I've heard it could be a bad bearing in the alternator, or a bad tensioner. Has this happened to anyone on here? Any advice would be a huge help. Thank you.
Installed 3g Alternator, Screeching Noise On Start Up.
- Thread starter 5point0dude
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Shakerhood
Dirt-Old 20+Year Member
Is it a used or new Alt? BTW, even though it has nothing to do with your problem I would install a smaller fuse than 200 Amps.
mikestang63
SN Certified Technician
Did you have the alternator tested prior to install? Sounds like you didn't. I would bring the car over to autozone and they can test it for free.
If the car did not make the noise prior to the 3g install then it is obviously related to that. You should use the 2g pulley as it is smaller than the 3g.Sometimes that is normal when you do a 3g install as the 3g alternator pulley does not line up perfectly and you may need to shim out the alternator or pulley. Take the belt off and spin the alternator,tensioner idler , smog, A/C pulleys by hand to see if you can isolate the noise. If you hear the alternator squeak or a loud whirring noise, the bearings are likely shot.
If the car did not make the noise prior to the 3g install then it is obviously related to that. You should use the 2g pulley as it is smaller than the 3g.Sometimes that is normal when you do a 3g install as the 3g alternator pulley does not line up perfectly and you may need to shim out the alternator or pulley. Take the belt off and spin the alternator,tensioner idler , smog, A/C pulleys by hand to see if you can isolate the noise. If you hear the alternator squeak or a loud whirring noise, the bearings are likely shot.
It was listed as a brand new alternator and the site I bought it from claims all there products are brand new, but now I don't know if I can believe that. Yeah, I installed the 4g power wire from PA Performance that is sold on LRS.com. Thought it would be easier because it's a complete kit.
No, I did not have it tested before I installed it, I'm definitely going to do that as soon as possible. And yes I do have the 2G pulley on right now.The more I think about it it does sound like a bad bearing, and if it is I'm glad it came with a 1-year warranty.
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